U.S. patent application number 15/977008 was filed with the patent office on 2018-11-22 for photovoltaic devices having rough metal surfaces.
The applicant listed for this patent is Alliance for Sustainable Energy, LLC. Invention is credited to David Charles Bobela, Scott Alan Mauger, Marinus Franciscus Antonius Maria van Hest, James Bacon Whitaker.
Application Number | 20180337293 15/977008 |
Document ID | / |
Family ID | 64272545 |
Filed Date | 2018-11-22 |
United States Patent
Application |
20180337293 |
Kind Code |
A1 |
Bobela; David Charles ; et
al. |
November 22, 2018 |
PHOTOVOLTAIC DEVICES HAVING ROUGH METAL SURFACES
Abstract
The present disclosure relates to a device that includes, in
order, a metal layer that includes aluminum, a first layer that
includes a titanium oxide, a second layer that includes zinc oxide,
and an absorber layer that includes indene-C60
bisadduct:poly(3-hexylthiophene) (ICBA:P3HT), where the metal layer
has a thickness between one micrometer and 30 .mu.m, and the metal
layer has a roughness greater than 10 nm.
Inventors: |
Bobela; David Charles;
(Golden, CO) ; van Hest; Marinus Franciscus Antonius
Maria; (Lakewood, CO) ; Mauger; Scott Alan;
(Arvada, CO) ; Whitaker; James Bacon; (Denver,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alliance for Sustainable Energy, LLC |
Golden |
CO |
US |
|
|
Family ID: |
64272545 |
Appl. No.: |
15/977008 |
Filed: |
May 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62507542 |
May 17, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/02363 20130101;
H01L 31/0392 20130101; H01L 51/441 20130101; H01L 51/00 20130101;
H01L 31/186 20130101; H01L 51/4253 20130101; Y02E 10/549 20130101;
H01L 31/0725 20130101 |
International
Class: |
H01L 31/0236 20060101
H01L031/0236; H01L 31/0392 20060101 H01L031/0392; H01L 31/0725
20060101 H01L031/0725; H01L 31/18 20060101 H01L031/18 |
Goverment Interests
CONTRACTUAL ORIGIN
[0002] The United States Government has rights in this invention
under Contract No. DEAC36-08G028308 between the United States
Department of Energy and Alliance for Sustainable Energy, LLC, the
Manager and Operator of the National Renewable Energy Laboratory.
Claims
1. A device comprising, in order: a metal layer comprising
aluminum; a first layer comprising a titanium oxide; a second layer
comprising zinc oxide; and an absorber layer comprising indene-C60
bisadduct:poly(3-hexylthiophene) (ICBA:P3HT), wherein: the metal
layer has a thickness between one micrometer and 30 .mu.m, and the
metal layer has a roughness greater than 10 nm.
2. The device of claim 1, wherein the thickness is between 10 .mu.m
and 20 .mu.m.
3. The device of claim 1, wherein the roughness is between 400 nm
and 2 .mu.m.
4. The device of claim 1, further comprising a substrate, wherein
the metal layer is positioned between the first layer and the
substrate.
5. The device of claim 4, wherein the substrate comprises
polyethylene naphthalate (PEN).
6. The device of claim 1, further comprising a third layer, wherein
the absorber layer is positioned between the third layer and the
second layer.
7. The device of claim 6, wherein the third layer comprises
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate
(PEDOT:PSS).
8. The device of claim 7, further comprising a fourth layer,
wherein the third layer is positioned between the fourth layer and
the absorber layer.
9. The device of claim 8, wherein the fourth layer comprises indium
zinc oxide.
10. A device comprising, in order: a metal layer comprising
aluminum; a first layer comprising a titanium oxide; and an
absorber layer comprising phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT), wherein: the metal layer
has a thickness between one micrometer and 30 .mu.m, and the metal
layer has a roughness greater than 10 nm.
11. The device of claim 10, wherein the thickness is between 10
.mu.m and 20 .mu.m.
12. The device of claim 10, wherein the roughness is between 400 nm
and 2 .mu.m.
13. The device of claim 10, further comprising a substrate, wherein
the metal layer is positioned between the first layer and the
substrate.
14. The device of claim 13, wherein the substrate comprises
polyethylene naphthalate (PEN).
15. The device of claim 10, further comprising a second layer,
wherein the absorber layer is positioned between the first layer
and the second layer.
16. The device of claim 15, wherein the second layer comprises
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate
(PEDOT:PSS).
17. The device of claim 15, further comprising a third layer,
wherein the second layer is positioned between the third layer and
the absorber layer.
18. The device of claim 17, wherein the third layer comprises
indium zinc oxide.
19. A method of fabricating a photovoltaic device, the method
comprising: depositing a first layer comprising at least one of
titanium or a titanium oxide on a metal layer, wherein the metal
layer has a roughness greater than 400 nm; depositing a second
layer comprising zinc oxide on the first layer; and depositing an
absorber layer on the second layer.
20. A method of fabricating a photovoltaic device, the method
comprising: depositing a first layer comprising at least one of
titanium or TiO.sub.x on a metal layer, wherein the metal foil has
a roughness greater than 400 nm; and depositing a bulk
heterojunction layer comprising an absorber layer on the first
layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/507,542 filed May 17, 2017, the contents
of which are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to thin film photovoltaic (PV)
devices, which may be based on organic, inorganic, and/or hybrid
materials. Related art thin film PV devices may be fabricated on
thin, inexpensive, and flexible metal or plastic substrates such as
stainless steel, polyethylene naphthalate (PEN) or polyethylene
terephthalate (PET) and may be deposited by inexpensive and rapid
roll-to-roll processing techniques. These advantages carve out
unique niche applications for thin film PV devices.
[0004] Related art thin film PV devices may include a smooth metal
surface that is formed on the substrate. However, it is expensive,
time-consuming, and energy-intensive to deposit the smooth metal
surface. In contrast, it would be advantageous to deposit a metal
layer on the substrate or to use a metal layer as the bottom
contact for the absorber layer, due to the low cost of the metal
layer as compared to screen-printed or evaporated metals. However,
the rough surface texture of the metal layer can degrade the
performance of thin film PV devices, most notably by lowering the
open circuit voltage.
SUMMARY
[0005] An aspect of the present disclosure is a device that
includes, in order, a metal layer that includes aluminum, a first
layer that includes a titanium oxide, a second layer that includes
zinc oxide, and an absorber layer that includes indene-C60
bisadduct:poly(3-hexylthiophene) (ICBA:P3HT), where the metal layer
has a thickness between one micrometer and 30 .mu.m, and the metal
layer has a roughness greater than 10 nm.
[0006] In some embodiments of the present disclosure, the thickness
may be between 10 .mu.m and 20 .mu.m. In some embodiments of the
present disclosure, the roughness may be between 400 nm and 2
.mu.m. In some embodiments of the present disclosure, the device
may further include a substrate, where the metal layer is
positioned between the first layer and the substrate. In some
embodiments of the present disclosure, the substrate may include
polyethylene naphthalate (PEN). In some embodiments of the present
disclosure, the device may further include a third layer, where the
absorber layer is positioned between the third layer and the second
layer. In some embodiments of the present disclosure, the third
layer may include poly(3,4-ethylenedioxythiophene) polystyrene
sulfonate (PEDOT:PSS). In some embodiments of the present
disclosure, the device may further include a fourth layer, where
the third layer is positioned between the fourth layer and the
absorber layer. In some embodiments of the present disclosure, the
fourth layer may include indium zinc oxide.
[0007] An aspect of the present disclosure is a device that
includes, in order, a metal layer that includes aluminum, a first
layer that includes a titanium oxide, and an absorber layer that
includes phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT), where the metal layer has
a thickness between one micrometer and 30 .mu.m, and the metal
layer has a roughness greater than 10 nm.
[0008] In some embodiments of the present disclosure, the thickness
may be between 10 .mu.m and 20 .mu.m. In some embodiments of the
present disclosure, the roughness may be between 400 nm and 2
.mu.m. In some embodiments of the present disclosure, the device
may further include a substrate, where the metal layer is
positioned between the first layer and the substrate. In some
embodiments of the present disclosure, the substrate may include
polyethylene naphthalate (PEN). In some embodiments of the present
disclosure, the device may further include a second layer, where
the absorber layer is positioned between the first layer and the
second layer. In some embodiments of the present disclosure, the
second layer may include poly(3,4-ethylenedioxythiophene)
polystyrene sulfonate (PEDOT:PSS). In some embodiments of the
present disclosure, the device may further include a third layer,
where the second layer is positioned between the third layer and
the absorber layer. In some embodiments of the present disclosure,
the third layer may include indium zinc oxide.
[0009] An aspect of the present disclosure is a method of
fabricating a photovoltaic device, where the method includes
depositing a first layer that includes at least one of titanium or
a titanium oxide on a metal layer, where the metal layer has a
roughness greater than 400 nm, depositing a second layer that
includes zinc oxide on the first layer, and depositing an absorber
layer on the second layer. An aspect of the present disclosure is a
method of fabricating a photovoltaic device, where the method
includes depositing a first layer that includes at least one of
titanium or TiO.sub.x on a metal layer, where the metal foil has a
roughness greater than 400 nm, and depositing a bulk heterojunction
layer that includes an absorber layer on the first layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows the structure of a thin film PV device,
according to some embodiments of the disclosure.
[0011] FIG. 2 shows the current density as a function of applied
voltage for various organic photovoltaic (OPV) devices, according
to some embodiments of the disclosure.
[0012] FIG. 3 shows the current density as a function of applied
voltage for additional OPV devices, according to some embodiments
of the disclosure.
REFERENCE NUMERALS
TABLE-US-00001 [0013] 100 OPV device 110 substrate 120 metal layer
130 first layer 140 second layer 150 absorber layer 160 third layer
170 fourth layer
DETAILED DESCRIPTION
[0014] FIG. 1 shows a diagram of the structure of a thin film PV
device, according to some embodiments of the present disclosure.
The thicknesses of the layers shown in FIG. 1 are not drawn to
scale. Although the layers are shown as being in direct contact
with each other, additional materials or layers may be present
between the layers that are shown in FIG. 1.
[0015] As shown in FIG. 1, the thin film PV device 100 may include
a substrate 110 that is made of a flexible material. For example,
the substrate 110 may be made of a polymer material, such as PEN or
PET. A metal layer 120 (e.g. a metal foil) may be formed on the
substrate 110. The metal layer 120 may be laminated to the
substrate 110, and may be made of at least one of aluminum, silver,
gold, molybdenum, and/or copper. The metal layer 120 may have any
suitable thickness, such as 13 .mu.m (0.5 mil), or between 1 .mu.m
and 30 .mu.m. The surface of the metal layer 120 opposite to the
substrate 110 may have a roughness that is greater than 400 nm, or
between 400 nm and 2 .mu.m. When compared to the roughness of metal
layers deposited by vapor deposition methods, e.g. between 1 nm and
10 nm, or between 1 nm and 3 nm, aluminum foils according to some
embodiments of the present disclosure, will have significantly
higher roughness values (e.g. greater than 400 nm). In some
embodiments of the present disclosure, a "rough" surface may be
characterized as a surface having a roughness value greater than 10
nm, whereas a "smooth" surface may be characterized as a surface
having a roughness value of less than or equal to 10 nm. As used
herein, the term "roughness" is defined as the maximum difference
in height between a peak and an adjacent valley on the surface of
the metal layer 120. In an alternative embodiment, the thin film PV
device may be formed without the substrate 110, such that the metal
layer 120 is the bottom layer of the thin film PV device.
[0016] Some related art methods deposit a zinc oxide (ZnO)
electron-selective layer on the metal layer 120 from a solution
phase. In some embodiments of the present disclosure, other
suitable conductive materials may be used, such as indium tin
oxide. However, this solution phase deposition may not uniformly
cover the rough surface of the metal layer 120, resulting in thinly
coated or non-coated areas that act as shunt paths for current,
thereby reducing the performance of the thin film PV device. It
should also be noted that ZnO will not form on an aluminum surface,
regardless of the roughness, from a precursor solution.
[0017] Accordingly, exemplary embodiments of the invention deposit
a first layer 130 of titanium and/or titanium oxide (TiO.sub.x)
onto a metal layer 120. For example, titanium may be deposited from
the vapor phase at evaporation rates up to 2 .ANG./sec, and the
resulting first layer 130 may have a thickness up to 25 nm. If
exposed to atmosphere, the titanium may oxidize to form titanium
dioxide (TiO.sub.2) or another oxide (TiO.sub.x). Alternatively,
TiO.sub.x may be deposited on a metal layer 120 by sputtering. As
discussed in further detail below, the first layer 130 of titanium
and/or TiO.sub.x allows a thin film PV device having the metal
layer 120 with a rough surface to achieve high performance.
[0018] A second layer 140 of zinc oxide (ZnO) may then be deposited
on the first layer 130. For example, ZnO may be spin-coated from a
solution that includes Zn, such as diethylzinc (DEZ) and/or zinc
acetate. The second layer 140 may have any suitable thickness, such
as a dry thickness of approximately 50 nm.
[0019] As shown in FIG. 1, an absorber layer 150 may be deposited
on the second layer 140. The absorber layer 150 may include an
organic material, an inorganic material, and/or a perovskite
material as an absorber material. For example, the absorber layer
150 may include phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT) and/or indene-C60
bisadduct : poly(3-hexylthiophene) (ICBA:P3HT). In order to
complete the PV device, a third layer 160 may then be deposited on
the absorber layer 150. The third layer 160 may be made of a
polymer material, such as poly(3,4-ethylenedioxythiophene)
polystyrene sulfonate (PEDOT:PSS). Further, a fourth layer 170 may
be deposited on the third layer 160. The fourth layer 170 may be
made of a transparent conductor. For example, the fourth layer 170
may include nanowires, nanotubes, organic conductors, and/or a
transparent conducting oxide (TCO), such as indium zinc oxide (IZO)
or indium tin oxide (ITO).
[0020] Table 1 summarizes various devices that were constructed and
tested, according to some embodiments of the present
disclosure.
TABLE-US-00002 TABLE 1 Device Architectures A B C D E F Fourth
layer IZO IZO IZO IZO IZO IZO (170) Third layer PEDOT: PEDOT:
PEDOT: PEDOT: PEDOT: PEDOT: (160) PSS PSS PSS PSS PSS PSS Absorber
PCBM: PCBM: PCBM: ICBA: ICBA: ICBA: (150) P3HT P3HT P3HT P3HT P3HT
P3HT Second layer NA NA NA NA ZnO ZnO (140) First layer ZnO
TiO.sub.x TiO.sub.x TiO.sub.x TiO.sub.x TiO.sub.x (130) Metal layer
smooth smooth rough smooth smooth rough (120) Al Al Al Al Al Al
Metal layer 0.150 0.150 13 0.150 0.150 13 thickness [.mu.m] Metal
layer <5 nm <5 nm >1 .mu.m <5 nm <5 nm >1 .mu.m
roughness Substrate glass glass PEN glass glass PEN (110)
[0021] FIG. 2 shows the current density as a function of applied
voltage for various OPV devices 100. As shown in FIG. 2, a first
OPV device (B), which included a glass substrate, a smooth aluminum
layer, a TiO.sub.x layer, a PCBM:P3HT layer, a PEDOT:PSS layer, and
an IZO layer. The smooth aluminum layer in the first OPV device (B)
was a thermally evaporated thin film. A second OPV device (A)
included a glass substrate, a smooth aluminum layer, a ZnO layer, a
PCBM:P3HT layer, a PEDOT:PSS layer, and an IZO layer. A third OPV
device (C), according to some embodiments of the present
disclosure, included a PEN substrate, a rough aluminum foil layer,
a TiO.sub.x layer, a PCBM:P3HT layer, a PEDOT:PSS layer, and an IZO
layer. Unexpectedly, despite the use of a rough aluminum metal
layer (e.g. a metal foil), the performance of the third OPV device
(C) was comparable to the performance of the first OPV device (B),
which used a comparatively smooth aluminum metal layer. For
example, OPV devices (C) and (B) have comparable fill factors and
open-circuit voltages. Further, FIG. 2 shows that it is not
necessary to include the ZnO layer to achieve a high-performance PV
device with a rough aluminum foil and a PCBM-based bulk
heterojunction layer.
[0022] FIG. 3 shows the current density as a function of applied
voltage for three additional OPV devices 100. As shown in FIG. 3, a
fourth OPV device (E), which included a glass substrate, a smooth
aluminum layer, a TiO.sub.x layer, a ZnO layer, an ICBA:P3HT layer,
a PEDOT:PSS layer, and an IZO layer. A fifth OPV device (D)
included a glass substrate, a smooth aluminum layer, a TiO.sub.x
layer, an ICBA:P3HT layer, a PEDOT:PSS layer, and an IZO layer. A
sixth OPV device (F), according to some embodiments of the present
disclosure, included a PEN substrate, an aluminum foil layer, a
TiO.sub.x layer, a ZnO layer, an ICBA:P3HT layer, a PEDOT:PSS
layer, and an IZO layer. Unexpectedly, despite the use of a rough
aluminum metal layer (e.g. a metal foil), the performance of the
sixth OPV device (F) was comparable to the performance of the
fourth related art OPV device, which used smooth aluminum
layers.
[0023] As discussed above, the absorber layer 150 may include
PCBM:P3HT and/or ICBA:P3HT. Due to the increased highest occupied
molecular orbital (HOMO)--lowest unoccupied molecular orbital
(LUMO) gap in the ICBA:P3HT material compared with the PCBM:P3HT
material, using ICBA:P3HT may provide an increase in the
open-circuit voltage of the OPV device. When using PCBM:P3HT as the
absorber layer 150, the Ti/TiO.sub.x layer suffices to give nearly
the full open-circuit voltage of approximately 580 mV. However,
when using the ICBA:P3HT as the absorber layer 150, including the
ZnO layer produces higher open-circuit voltages than the
Ti/TiO.sub.x layer alone. This OPV device may achieve open-circuit
voltages of at least 700 mV, such as 780 mV. FIG. 3 also shows that
the ZnO layer should be included to achieve a high-performance PV
device with a rough aluminum foil and an ICBA-based bulk
heterojunction layer.
[0024] Without wishing to be bound by theory, FIG. 2 and FIG. 3
demonstrate that using ZnO directly on aluminum does not result in
a functional device presumably due to the formation of a resistant
Al.sub.2O.sub.3 layer between the ZnO and aluminum, causing the
device performance to be poor (e.g. low FF). However, the titanium
layer appears to eliminate and/or reduce the formation of this
resistant Al.sub.2O.sub.3 layer. Although aluminum does typically
have an oxide component, the addition of titanium to the aluminum
may create an aluminum/Al.sub.2O.sub.3/titanium combination of
layers. However, without wishing to be bound by the theory, the
titanium may subsequently claim the oxygen from the Al.sub.2O.sub.3
resulting in a transformation of the titanium metal to a titanium
oxide (TiO.sub.x) and an Al/TiO.sub.x/Ti combination of layers,
which is a better conductor than Al.sub.2O.sub.3.
[0025] In addition, it appears that the energy levels of TiO.sub.x
are not correct for ICBA based absorbers. However, the deposition
of ZnO on the TiO.sub.x remedies this problem, resulting in a
better performing device (see OPV devices (E) and (F) of FIG. 3).
In the case of rough metals, where uniform coverage is a challenge,
and where ICBA exposed directly to Al/Al.sub.2O.sub.3 performs
poorly, the evaporation of titanium onto the aluminum prevent
direct contact between the absorber and the `metal`. Some exposure
by the absorber layer to the TiO.sub.x is fine as long as most of
the absorber layer contacts ZnO, making the energy contacts. Hence,
OPV devices (E) and (F) demonstrated very similar performances.
EXPERIMENTAL
[0026] Smooth aluminum layers: deposited by thermal evaporation to
a target thickness of about 150 nm. Evaporation rate was 2.0
.ANG./s. Deposition pressure was 1.8 e-7 torr.
[0027] TiO.sub.x layers: deposited titanium metal layers by thermal
evaporation to a target thickness of about 10 nm. Evaporation rate
was between 0.3 .ANG./S and 1.8 .ANG./S. Deposition pressure was
1.6 e.sup.-7 torr. Converted the titanium metal layers to TiO.sub.x
layers by exposure to air for several hours.
[0028] P3HT:PCBM/ICBA layers: 1:1 wt in ortho-dichlorobenzene. 50
mg/mL total solids. Spin coated 60 .mu.L at 700 rpm for 60 seconds
in a N.sub.2 glove box. A final thickness of about 250 nm was
targeted for all OPV devices made.
[0029] PEDOT:PSS layers: spin coated in air. 350 .mu.L at 4000 rpm
for 60 seconds. Annealed at 150.degree. C. for 5 minutes in
N.sub.2. Used Clevios HTL Solar version but could have used others
with surfactants. A final thickness of about 50 nm was
targeted.
[0030] ZnO layers: Solution was one part diethylzinc in toluene (15
wt %) to 3 parts tetrahydrofuran. Spin coated in air--250 .mu.L at
7000 rpm for 30 s. Annealed in air at 120.degree. C. for 20
minutes. A final thickness of about 40 nm was targeted.
EXAMPLES
Example 1
[0031] A device comprising, in order: a metal layer; a first layer
comprising a titanium oxide; a second layer comprising zinc oxide;
and an absorber layer.
Example 2
[0032] The device of claim 1, wherein the metal layer comprises at
least one of aluminum, silver, gold, molybdenum, or copper.
Example 3
[0033] The device of claim 2, wherein the metal layer comprises
aluminum.
Example 4
[0034] The device of claim 1, wherein the metal layer has a
thickness between one micrometer and 30 .mu.m.
Example 5
[0035] The device of claim 4, wherein the thickness is between 10
.mu.m and 20 .mu.m.
Example 6
[0036] The device of claim 1, wherein the metal layer has a
roughness of greater than 10 nm.
Example 7
[0037] The device of claim 6, wherein the roughness is greater than
100 nm.
Example 8
[0038] The device of claim 7, wherein the roughness is between 400
nm and 2 .mu.m.
Example 9
[0039] The device of claim 1, wherein the absorber layer comprises
indene-C60 bisadduct:poly(3-hexylthiophene) (ICBA:P3HT).
Example 10
[0040] The device of claim 1, further comprising a substrate,
wherein the metal layer is positioned between the first layer and
the substrate.
Example 11
[0041] The device of claim 10, wherein the substrate comprises
polyethylene naphthalate (PEN).
Example 12
[0042] The device of claim 1, further comprising a third layer,
wherein the absorber layer is positioned between the third layer
and the second layer.
Example 13
[0043] The device of claim 12, wherein the third layer comprises
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate
(PEDOT:PSS).
Example 14
[0044] The device of claim 12, further comprising a fourth layer,
wherein the third layer is positioned between the fourth layer and
the absorber layer.
Example 15
[0045] The device of claim 14, wherein the fourth layer comprises
indium zinc oxide.
Example 16
[0046] The device of claim 1, wherein: the absorber layer comprises
indene-C60 bisadduct:poly(3-hexylthiophene) (ICBA:P3HT), the metal
layer comprises aluminum, the metal layer has a thickness between
10 .mu.m and 20 .mu.m, and the metal layer has a roughness between
400 nm and 2 .mu.m.
Example 17
[0047] A device comprising, in order: a metal layer; a first layer
comprising a titanium oxide; and an absorber layer.
Example 18
[0048] The device of claim 17, wherein the metal layer comprises at
least one of aluminum, silver, gold, molybdenum, or copper.
Example 19
[0049] The device of claim 18, wherein the metal layer comprises
aluminum.
Example 20
[0050] The device of claim 17, wherein the metal layer has a
thickness between one micrometer and 30 .mu.m.
Example 21
[0051] The device of claim 20, wherein the thickness is between 10
.mu.m and 20 .mu.m.
Example 22
[0052] The device of claim 17, wherein the metal layer has a
roughness of greater than 10 nm.
Example 23
[0053] The device of claim 22, wherein the roughness is greater
than 100 nm.
Example 24
[0054] The device of claim 23, wherein the roughness is between 400
nm and 2 .mu.m.
Example 25
[0055] The device of claim 17, wherein the absorber layer comprises
phenyl-C61-butyric acid methyl ester:poly(3-hexylthiophene)
(PCBM:P3HT).
Example 26
[0056] The device of claim 17, further comprising a substrate,
wherein the metal layer is positioned between the first layer and
the substrate.
Example 27
[0057] The device of claim 26, wherein the substrate comprises
polyethylene naphthalate (PEN).
Example 28
[0058] The device of claim 17, further comprising a second layer,
wherein the absorber layer is positioned between the first layer
and the second layer.
Example 29
[0059] The device of claim 28, wherein the second layer comprises
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate
(PEDOT:PSS).
Example 30
[0060] The device of claim 28, further comprising a third layer,
wherein the second layer is positioned between the third layer and
the absorber layer.
Example 31
[0061] The device of claim 30, wherein the third layer comprises
indium zinc oxide.
Example 32
[0062] The device of claim 17, wherein: the absorber layer
comprises phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT), the metal layer comprises
aluminum, the metal layer has a thickness between 10 .mu.m and 20
.mu.m, and the metal layer has a roughness between 400 nm and 2
.mu.m.
Example 33
[0063] A method of fabricating a photovoltaic device, the method
comprising: depositing a first layer comprising at least one of
titanium or a titanium oxide on a metal layer, wherein the metal
layer has a roughness greater than 400 nm; depositing a second
layer comprising zinc oxide on the first layer; and depositing an
absorber layer on the second layer.
Example 34
[0064] The method of claim 33, wherein the first layer is deposited
from a vapor phase.
Example 35
[0065] The method of claim 33, wherein the second layer is
spin-coated from a solution comprising Zn.
Example 36
[0066] The method of claim 33, wherein the metal layer comprises
aluminum.
Example 37
[0067] The method of claim 33, wherein the absorber material
comprises at least one of phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT) or indene-C60
bisadduct:poly(3-hexylthiophene) (ICBA:P3HT).
Example 38
[0068] The method of claim 37, wherein the absorber material
comprises ICBA:P3HT.
Example 39
[0069] The method of claim 33, further comprising: depositing a
third layer comprising a polymer material on the bulk
heterojunction layer; and depositing a fourth layer comprising a
transparent conductor on the third layer.
Example 40
[0070] A method of fabricating a photovoltaic device, the method
comprising: depositing a first layer comprising at least one of
titanium or TiO.sub.x on a metal layer, wherein the metal foil has
a roughness greater than 400 nm; and depositing a bulk
heterojunction layer comprising an absorber material on the first
layer.
Example 41
[0071] The method of claim 40, wherein the first layer is deposited
from a vapor phase.
Example 42
[0072] The method of claim 40, wherein the metal layer comprises
aluminum.
Example 43
[0073] The method of claim 40, wherein the absorber material
comprises at least one of phenyl-C61-butyric acid methyl
ester:poly(3-hexylthiophene) (PCBM:P3HT) or indene-C60
bisadduct:poly(3-hexylthiophene) (ICBA:P3HT).
Example 44
[0074] The method of claim 40, further comprising: depositing a
third layer comprising a polymer material on the bulk
heterojunction layer; and depositing a fourth layer comprising a
transparent conductor on the third layer.
[0075] The foregoing discussion and examples have been presented
for purposes of illustration and description. The foregoing is not
intended to limit the aspects, embodiments, or configurations to
the form or forms disclosed herein. In the foregoing Detailed
Description for example, various features of the aspects,
embodiments, or configurations are grouped together in one or more
embodiments, configurations, or aspects for the purpose of
streamlining the disclosure. The features of the aspects,
embodiments, or configurations, may be combined in alternate
aspects, embodiments, or configurations other than those discussed
above. This method of disclosure is not to be interpreted as
reflecting an intention that the aspects, embodiments, or
configurations require more features than are expressly recited in
each claim. Rather, as the following claims reflect, inventive
aspects lie in less than all features of a single foregoing
disclosed embodiment, configuration, or aspect. While certain
aspects of conventional technology have been discussed to
facilitate disclosure of some embodiments of the present invention,
the Applicants in no way disclaim these technical aspects, and it
is contemplated that the claimed invention may encompass one or
more of the conventional technical aspects discussed herein. Thus,
the following claims are hereby incorporated into this Detailed
Description, with each claim standing on its own as a separate
aspect, embodiment, or configuration.
* * * * *